1. Field of the Invention
The present invention relates to an optical signal recording/playback apparatus that records or plays back various types of information recorded on an optical recording medium such as an optical disk, and a recording compensation method and a playback method which are used therefor.
2. Description of the Related Art
Conventionally, various optical-signal recording/playback apparatuses using optical disks have been provided. These apparatuses include playback-only apparatuses using playback-only optical disks such as compact disks (CDs), and recording and playback apparatuses using rewritable optical disks such as magnetooptical disks and phase-change disks. In this description, disks in accordance with different types of formats are collectively referred to as “optical disks”.
A method in which data coded by a data coding system having a predetermined mark-length limitation is recorded on an optical disk, as disclosed in Japanese Unexamined Patent Application Publication No. 10-283636, is known as one of signal recording methods for the above optical-signal recording/playback apparatuses.
In this method, signals are recorded on or played back from an optical disk by setting the shortest mark length as 2T and the longest mark length as 8T when each mark length is represented by a multiple of a recording-pulse period T.
For increasing the density of recording signals in the track direction of the optical disk in the above optical-signal recording/playback apparatuses, interference (crosstalk) and destruction (cross-write/cross-erase) between adjacent tracks must be prevented. These cause inability in increasing the density.
For example, in optical modulating recording that outputs modulated light by controlling the switching of a light source, when a long mark is recorded, storage of heat laterally expands each optical spot, thus increasing crosstalk and cross-erase.
In addition, in magnetooptically magnetic-modulating recording, when a long mark is recorded, a leakage magnetic field is enhanced and operates as an applied magnetic field bias for recording. This hinders preferable recording.